Method and device for the separate three-dimensional representation of the arterial and venous vascular system using C-arm angiography systems

ABSTRACT

The invention relates to a method and a device for the separate three-dimensional representation of arteries and/or veins in a vascular system of the body by means of a C-arm biplanar system having two C-arms, which can each record a sequence of x-ray images from different projection angles during a mask or filler pass. With the filler pass, both C-arms record x-ray images, so that the x-ray images of the filler pass can be combined to form a first data record, which contains x-ray images from the arterial phase of the vascular contrasting and/or to form a second data record, which contains x-ray images from the venous phase of the vascular contrasting. This enables the arterial and venous phases to be reconstructed separately.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of German application No. 10 2006 040934.5 filed Aug. 31, 2006, which is incorporated by reference herein inits entirety.

FIELD OF THE INVENTION

The present invention relates to a method for the separatethree-dimensional representation of arteries and/or veins of a vascularsystem in a part of the body of a vertebrate using a C-arm biplanarsystem, in other words an x-ray angiography system having two C-armswhich can be moved about a patient bed, into which an x-ray recordingsystem is integrated in each instance.

BACKGROUND OF THE INVENTION

There is an increasing demand for the most accurate possiblethree-dimensional representation of the appearance and pattern ofvessels in parts of the body, in particular of arteries and veins, fordiagnostic purposes within the field of vascular diseases and thetherapy thereof. The examination of cerebral aneurysms represents animportant field of application, this also includes an analysis andoptimal representation for defining the aneurysm neck usingtopographical relations with adjacent vessels. Angiographs are alsocarried out on different parts of the body, in order to determinearteriosclerotic changes or deformities. The introduction ofcomputer-aided rotation angiography, which reconstructsthree-dimensional representations with an equal resolution from theprojection raw data, achieves a technical breakthrough within the fieldof diagnostics. The so-called C-arm angiographs form here the prior art,in which an x-ray source and an x-ray detector arranged on a C-arm andopposite thereto, are rotated about the part of the body of a patient tobe examined in an arc encompassing approximately 200° and between 50 and500 x-ray images are recorded here and digitally stored. Athree-dimensional model of the x-rayed part of the body can becalculated from x-ray images recorded from different projection angles.The conventional 3D angiography nevertheless fails to ensure anadequately clear separation between the arterial and venous vascularsystems, by virtue of the recording times and the dynamics of thecontrast agent propagation.

With the afore-described three-dimensional vascular representation, aso-called mask pass and a filler pass are recorded. During the “maskpass”, the C-arm rotates about the part of the body of the patient orthe whole patient and records a first sequence of x-ray images withoutcontrasting over the predetermined angular range. A contrast agent isthen injected into the vessel of interest and with another C-armrotation, the so-called “filler pass”, a second sequence of x-ray imagesis recorded. The two sequences are now subtracted from each other suchthat only the contrasted vessels (i.e. containing contrast agent) canstill be seen in the result. These are now reconstructed to form athree-dimensional image data record using a 3D reconstruction method.Alternatively, masks and filler pass sequences can also be reconstructedseparately and the resulting three-dimensional data records aresubtracted from one another.

The 3D angiography method according to the prior art generally providesa three-dimensional image data record, which represents both a part ofthe arterial vascular system as well also as parts of the venousvascular system. The reason for this flaw in current angiography systemscan be attributed to the rotation time of the C-arm of 5 s beingsignificantly longer than the arterial phase of the vascularcontrasting, which only lasts 2 to 3 seconds. The contrast agent thenpermeates over the conventional capillary paths into the venous vascularsystem so that a venous phase of the vascular contrasting is indicatedafter the arterial phase has passed, said vascular contrasting beingcharacterized in a subsequent part of the rotation of the tomographs,thereby resulting in a three-dimensional mixed structure of arteries andveins.

DE 102 41 184 A1 discloses a method for generating a volume data recordof an object using a first and a second x-ray system, with which a firstseries of 2D projections of the object is recorded with the first x-raysystem at projection angles which differ from one another, with thefirst x-ray system being rotated about an axis and scanning a firstangular range, and with which a second series of 2D projections of theobject are essentially recorded at the same time using the second x-raysystem at different projection angles from one another, with the secondx-ray system being rotated about an axis and scanning a second angularrange which differs from the first angular range.

SUMMARY OF THE INVENTION

The object underlying the present invention is thus to generatethree-dimensional image data records of vessels, which either onlyrepresent arteries or veins (depending on requirements).

This object is achieved in accordance with the invention by the methodfor the separate three-dimensional representation of arteries and/orveins as well as the device for separate three-dimensionalrepresentation as claimed in the independent claims.

Further advantageous embodiments, aspects and details of the presentinvention result from the dependent claims, the description and theappended drawings.

The knowledge underlying the invention is that twice as many x-rayimages can be acquired simultaneously using a C-arm biplanar system, inother words an x-ray angiography system with two C-arms, than with amonoplanar system, even though the readout speed of the x-ray detectorand the rotation speed of the C-arm are equally as great. The recordingtime for a single filler pass is thus halved compared with a monoplanarsystem. It is thus possible to record and reconstruct an arterial phaseof approximately two to three seconds (with current conventionalrotation times of four to five seconds per pass) in an isolated fashion.

In a first aspect, the invention is thus directed at a method for theseparate three-dimensional representation of arteries and/or veins of avascular system in a part of the body of a vertebrate using a C-armbiplanar system, comprising two C-arms, each of which can record asequence of x-ray images from different projection angles during a maskpass or a filler pass about the part of the body. The method ischaracterized by the following steps:

-   -   (a) Implementing a mask pass about a body part to be examined        prior to injecting contrast agent into the vertebrate, in which        at least one of the two C-arms records x-ray images;    -   (b) Implementing a filler pass about the part of the body after        injecting a contrast agent, in which the two C-arms of the        biplanar system in the rotation direction are offset against one        another by a differential angle, and in which x-ray images are        recorded with both C-arms;    -   (c) Combining the x-ray images of the filler pass of the first        and the second C-arm to form a first data record, which contains        x-ray images from the arterial phase of the vascular contrasting        and/or to form a second data record, which contains x-ray images        from the venous phase of the vascular contrasting; and    -   (d) Subtracting the data record obtained during the mask pass        from one of the first and/or second data records obtained during        the combination, in order to obtain at least one final data        record, which contains data relating to a three-dimensional        representation of the arterial or venous vascular system.

In terms of the present invention, a mask pass is a rotation pass of theC-arm x-ray device without the use of a contrast agent.

A filler pass is understood in accordance with the invention to mean arotation pass of the C-arm x-ray device, in which the cavity to beexamined, in this case vessels, are filled with a contrast agent to sucha degree that an adequate x-ray contrast results.

As is known to experts, a contrast agent is a substance, which isrelatively impermeable for x-rays and thus makes filled vessels visibleby a clear x-ray shading.

An injection of contrast agent is understood to mean the administrationof the contrast agent into the cavity to be examined and/or the vesselto be examined, by means of an injection for instance.

A combination of data from the filler passes to form data records isunderstood to mean that sub quantities of the x-ray images of the twoC-arms can be combined to form new data records, according topredetermined rules, which only contain x-ray images from the arterialand/or venous phase of the vessel contrasting, with the aid of apredetermined algorithm and if necessary under the influence of a humanevaluator. This can be achieved for instance in that the first half ofthe x-ray image sequence of each C-arm is assigned to the arterial phaseand the second half is assigned to the venous phase in each instance.

The differential angle between the two C-arms of the biplanar system isparticularly preferred at least during the filler pass of approximately90° plus the half fan angle of the C-arms. As a three-dimensional imagedata record can already be reconstructed from an x-ray sequence, whichcovers 180° plus the fan angle of the C-arm, a complete data record canalready be recorded with this differential angle with a rotation of theC-arm about 90° plus the half fan angle. The recording time is thushalved for an individual pass compared with the monoplanar system.

With the method according to the invention, as with the currentconventional monoplanar systems and also with the biplanar system, amask pass is first recorded without a contrast agent. For the mask pass,either both C-arms can be rotated in each instance about 90° plus thehalf fan angle or only one C-arm is rotated about 180° plus the fanangle. After injecting a contrast agent, a rotation is carried out withboth C-arms which is potentially delayed by a certain time, during whichthe contrast agent permeates into the part of the body of interest. Ifthe two C-arms are offset against one another by 90° plus the half fanangle, a rotation by 90° plus the half fan angle is preferably carriedout. The x-ray images recorded by the two C-arms during this filler passcan be combined to form a first data record, and thus produce a completedata record, from which a three-dimensional image data record can bereconstructed in the arterial phase. A three-dimensional image of thearterial vascular system is now obtained by subtracting the mask passfrom the filler pass and subsequently reconstructing, or byreconstructing the mask pass and the filler pass and then subtracting.

A further rotation of both C-arms about approximately 90° plus the halffan angle can preferably be carried out immediately after the arterialfiller pass has been recorded. This rotation can be carried out both inthe same direction as well as in an opposite direction, such as thefirst rotation of the filler pass. The x-ray images of the two C-armsthus obtained can be combined in a similar manner to form areconstructable second data record, which contains the venous phase ofthe vascular contrasting. A three-dimensional image data record of thevenous vascular system can be reconstructed from this data record, asdescribed above.

Alternatively to the above-described embodiment, in which the C-arms,during the filler pass, rotate in each instance only about approximately90° plus the half fan angle, the filler pass can also include a rotationof the two C-arms about approximately 180° plus the whole fan angle ofthe C-arms. In this way, the x-ray images of the first 90° plus the halffan angle of both C-arms are combined to form a first data record of thearterial phase, the images of the second 90° plus the half fan angle arecombined to form a second data record of the venous phase.

A mask pass is likewise also conceivable, in which both C-arms rotateabout 180° plus fan angle, with images only being recorded with one ofthe two C-arms.

In a preferred embodiment, the examined body part is a skull of aperson. One important field of application is herewith the locating ofaneurysms in the vessels of the brain. It is however clear that otherparts of the human body and other types of animal can essentially beaccessed using a vascular system according to the method of theinvention. The method has been restricted in accordance with theinvention to vertebrate, since these have a separate arterial and venousblood circulation, nevertheless it is clear that if necessary the methodcan also be applied with other classes of animal, provided these have acontrastable vascular system with arteries and veins.

In a further aspect, the invention is directed towards a device, withall that has been said in respect of the method also being valid to thedevice or vice versa, so that reference can be made alternately. Thedevice according to the invention for separate three-dimensionalrepresentation of arteries and/or veins of a vascular system in a partof a body of a vertebrate comprises a C-arm biplanar system, whichcomprises two C-arms, which are designed to record a sequence of x-rayimages from different projection angles in each instance during a maskor filler pass about the body part and is characterized by:

-   -   (a) a device for injecting a contrast agent into the vertebrate;    -   (b) a control device for controlling the two C-arms of the        biplanar system such that a mask pass about a part of the body        to be examined is first carried out without contrast agent, and        then a filler pass is carried out after injecting the contrast        agent, in which the two C-arms of the biplanar system are offset        against one another in the rotation direction about a        differential angle and whereby the x-rays are recorded using        both C-arms.    -   (c) a data storage device for storing the x-ray images obtained        during the mask pass and during the filler pass;    -   (d) a computing module for combining x-ray images of the filler        pass from the first and the second C-arm to form a first data        record, which contains x-ray images from the arterial phase of        the vascular contrasting and/or to form a second data record,        which contains x-ray images from the venous phase of the vessel        contrasting; and for subtracting the data record obtained during        the mask pass from a first and/or second data record obtained        during the combination in order to obtain at least one final        data record, which contains data for a three-dimensional        representation of the arterial or venous vascular system.

The device for injecting a contrast agent is preferably an automaticinjector, with which the time instant and the speed of the injection canbe precisely determined.

A control facility is the control module of a C-arm biplanar system forinstance. This can be integrated for example into a PC or suchlike.

A computing module is understood here to mean either a device, which isdesigned especially to perform calculations to be carried out, forinstance an analog computer or a digital signal processor with acorresponding controller, or a computer module is understood to mean asoftware program product, which implements the functionalities on auniversal computing system. A data memory device is understood to meanany device which is able to store digital data, be this a volatile orpermanent main memory, a hard disk, an optical data carrier etc. withaccess hereto being possible by the computing modules.

In a particularly preferred embodiment, the device is suited toimplementing the method according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is to be described in more detail below with reference toconcrete exemplary embodiments, with reference being made to appendeddrawings, in which the following is illustrated:

FIG. 1 shows the principle of the scanning of a patient body in a firstembodiment of the invention,

FIG. 2 shows the principle of the scanning of a patient body in a secondembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the first embodiment of the method according to theinvention, a rotation pass (mask or filler pass) of the C-arm biplanarsystem comprises approximately 180° plus the fan angle in each instance.In the illustration in FIG. 1, the upper row “plane A” shows therecording from the view of the first C-arm, the lower row “plane B”shows the recordings of the second C-arm, which, in the example shown,is offset compared with plane A by a differential angle of approximately90° plus a half fan angle, namely in the rotation direction.

In the left upper sub image of FIG. 1, the mask pass is shownschematically. This indicates a cross-sectional view of a patient 1. Thearrow 2 shows the rotation direction of the first C-arm and sector 3shows the detected projection angle of the mask pass. A completerotation pass about approximately 180° plus the fan angle is carried outcounter clockwise, with only the first C-arm (plane A) recording x-rayimages. The second C-arm can rotate or be stationary.

A filler pass is illustrated on the right-hand side, in which bothC-arms (Plane A and plane B) participate. At the start, a contrast agentis injected at time instant 7. Consequently, both C-arms rotate in thedirection of arrows 4 a, 4 b in a clockwise direction aboutapproximately 180° plus the fan angle. During the first half of thisfiller pass, the arterial phase 5 is detected, which is shown by ashaded sector 5 on the left. In the further course of this filler pass,the venous phase is used, which is shown in each instance by a shadedsector 6 on the right.

As is clear from FIG. 1, the sectors 5 of planes A and B can be combinedto form a complete data record, which covers more than 180°, namely 180°plus the fan angle. A three-dimensional image of the arterial phase canthus be reconstructed from the x-ray images recorded in the sectors 5.The same applies to the venous phase and the two sectors 6, which can,as a whole, be combined to form a reconstructable data record.

The embodiment in FIG. 1 thus requires two rotations of the biplanarsystem about 180° plus the fan angle in each instance. These can, asshown, occur in the opposite direction, they can however also occur inthe same direction. The system must however then rotate once by 360°about the patient 1, thereby potentially running into spatialdifficulties.

The embodiment in FIG. 2 by contrast only requires 90° rotations. Thisexemplary embodiment is thus preferable for systems which only allow arestricted rotation angle.

Both C-arms rotate about 90° plus the half fan angle in order to recordthe mask pass, as shown in both left illustrations of planes A and B inFIG. 2. During the rotation in the direction of arrows 2 a and 2 b, eachC-arm records a sector 3 of x-ray images in each instance, which aresubsequently combined to form a complete mask pass. After the contrastagent injection 7, both C-arms counter rotate about 90° plus the halffan angle along the arrows 4 a, 4 b in the opposite direction andherewith record the images of the arterial filler pass along the sectors5. The images of both sectors 5 can, as shown in exemplary embodiment 1,be combined to form a complete first data record in each instance, whichcontains x-ray images only from the arterial phase of the vascularcontrasting.

As shown in both right sub images, the two C-arms then rotate back in afurther rotation about 90° plus the half fan angle in the same directionas with the mask pass along arrows 8 a, 8 b and in doing so record x-rayimages of the venous phase along the sectors 6. The x-ray images ofsectors 6 are then combined to form a second data record, which containsx-ray images from the venous phase of the vascular contrasting. It isthus possible to obtain two final data records by subtracting the datarecord 3 obtained during the mask pass 2 a, 2 b, from the arterial datarecord of sectors 5 and the data record of sectors 6, said two finaldata records containing x-ray images which can be reconstructed to forma three-dimensional image data record of the arterial and/or venousvascular system. Alternatively, as mentioned above, the individual datarecords of the mask pass, the arterial and venous phase can also bereconstructed first to form a three-dimensional image data record, thesesubsequently being subtracted from one another.

The method according to the invention enables, with the aid of a C-armbiplane system, recording times for a reconstructable data recordcomprising x-ray images to be realized in less than 3 seconds. Thisenables three-dimensional image data records of the arterial and venousvascular system to be obtained without mutual superimposition.

1.-9. (canceled)
 10. A method for obtaining a separate x-ray data recordof arteries or venous of a vascular system in a part of a body of avertebrate using a biplanar C-arm system with a first C-arm and a secondC-arm, comprising: recording a mask pass x-ray data record of the partof the body during a mask pass of the C-arm system rotating about thepart of the body prior to injecting a contrast agent into thevertebrate; recording a first and a second filler pass x-ray datarecords of the part of the body during a filler pass of the C-arm systemrotating about the part of the body respectively recorded by the firstand the second C-arms after injecting the contrast agent into thevertebrate, wherein the first and the second C-arms are offset withrespective to each other about a differential angle in the rotationdirection; combining the first and the second filler pass x-ray datarecords to generate a first data record only comprising x-ray datarecords of the arteries and to generate a second data record onlycomprising x-ray data records of the veins; and subtracting the maskpass x-ray data record from the first or the second data record toobtain the separate data record of the arteries or the venous formedically examining the part of the body.
 11. The method as claimed inclaim 10, wherein the differential angle equals to 90° plus a half fanangle of the first and the second C-arms.
 12. The method as claimed inclaim 10, wherein the filler pass comprises a first rotation of theC-arms in a first direction about 90° plus a half fan angle of theC-arms and a second rotation of the C-arms in a second directionopposite to the first direction about 90° plus the half fan angle of theC-arms.
 13. The method as claimed in claim 10, wherein the filler passcomprises a rotation of the C-arms about 180° plus a fan angle of theC-arms.
 14. The method as claimed in claim 10, wherein a first half ofthe first and the second filler pass x-ray data records comprises onlythe x-ray data records of the arteries.
 15. The method as claimed inclaim 10, wherein a second half of the first and the second filler passx-ray data records comprises only the x-ray data records of the veins.16. The method as claimed in claim 10, wherein the mask pass comprises arotation of the C-arms about 90° plus a half fan angle of the C-arms andthe mask pass x-ray data record is recorded by both of the C-arms. 17.The method as claimed in claim 10, wherein the mask pass comprises arotation of the C-arms about 180° plus a fan angle of the C-arms and themask pass x-ray data records is recorded by one of the C-arms.
 18. Themethod as claimed in claim 10, wherein a three-dimensionalrepresentation is reconstructed prior to the step of combining, or priorto the step of subtracting, or after the step of subtracting.
 19. Themethod as claimed in claim 10, wherein the part of the body is a skullof the vertebrate.
 20. A device for obtaining a separate x-ray datarecord of arteries or veins of a vascular system in a body part of avertebrate using a biplanar C-arm system with a first C-arm and a secondC-arm, comprising: a device that injects a contrast agent into thevertebrate; a control device that controls the first and the secondC-arms so that: a mask pass x-ray data record of the part of the body isrecorded during a mask pass of the C-arm system rotating about the partof the body prior to injecting the contrast agent, a first and a secondfiller pass x-ray data records of the part of the body is recordedrespectively by the first and the second C-arms during a filler passrotating about the part of the body after injecting the contrast agent,wherein the first and the second C-arms are offset with respective toeach other in the rotation direction by a differential angle; and acomputing device that: combines the first and the second filler passx-ray data records to generate a first data record only comprising x-raydata records of the arteries and to generate a second data record onlycomprising x-ray data records of the veins, and subtracts the mask passx-ray data record from the first or the second data record to obtain theseparate data record of the arteries or the venous.
 21. The device asclaimed in claim 20, further comprising a data memory that stores themask pass x-ray data record and the first and the second filler passx-ray data records.
 22. The device as claimed in claim 20, wherein thecomputing device reconstructs a three-dimensional representation priorto the combining, or prior to the subtracting, or after the subtracting.23. The device as claimed in claim 20, wherein the differential angleequals to 90° plus a half fan angle of the first and the second C-arms.24. The device as claimed in claim 20, wherein the filler pass comprisesa first rotation of the C-arms in a first direction about 90° plus ahalf fan angle of the C-arms and a second rotation of the C-arms in asecond direction opposite to the first direction about 90° plus the halffan angle of the C-arms.
 25. The device as claimed in claim 20, whereinthe filler pass comprises a rotation of the C-arms about 180° plus a fanangle of the C-arms
 26. The device as claimed in claim 20, wherein afirst half of the first and the second filler pass x-ray data recordscomprises only the x-ray data records of the arteries.
 27. The device asclaimed in claim 20, wherein a second half of the first and the secondfiller pass x-ray data records comprises only the x-ray data records ofthe veins.
 28. The device as claimed in claim 20, wherein the mask passcomprises a rotation of the C-arms about 90° plus a half fan angle ofthe C-arms and the mask pass x-ray data record is recorded by both ofthe C-arms.
 29. The device as claimed in claim 20, wherein the mask passcomprises a rotation of the C-arms about 180° plus a fan angle of theC-arms and the mask pass x-ray data records is recorded by one of theC-arms.